Voltage converters are frequently designed as either step-up converters or step-down converters. If a voltage converter is connected on the input side to a battery whose voltage diminishes over time, it can be necessary to carry out a step-down conversion with a voltage converter designed for step-up conversion.
The document US 2004/0135556 A1 describes a DC/DC converter with an inductor and two switches. A first switch connects an output-side terminal of the inductor to a reference potential terminal. A second switch additionally connects the output-side terminal of the inductor to one output of the voltage converter. For step-down conversion, the first switch is alternately switched from the conductive state to the blocking state.
The document US 2008/0211467 A1 concerns a circuit for reducing oscillations in switching converters and shows various converters. One period can have three phases with different operating states.
The data sheet “AS1329 Low Voltage, Micro power, DC-DC Step-Up Converters”, austriamicrosystems AG, Austria, version 1.06, 2009 describes a step-up converter.
The document US 2003/0178974 A1 specifies a step-up/step-down voltage converter with an inductor and a first and second switch.